Methods of producing microporous zwitterionic cryogels are described, wherein the cryogels are useful for sustaining release of therapeutic agents. The disclosed cryogels overcome several limitations associated with existing compositions, for example the disclosed cryogels have high loading efficiencies and a sustained release profile with minimal burst of up to 4 months or more. The characteristics of the disclosed cryogels can be varied by altering monomer (e.g. zwitterion) and crosslinker selection. The amount of monomer contained in the hydrogel may also be varied to aid in controlling the cryogel's chemistry.
